1. Field of the Invention
This invention relates to downhole drilling and more particularly to downhole turbine sleeves and methods for making downhole turbine sleeves.
2. Description of the Related Art
Downhole drilling environments present some of the harshest conditions on the planet. Materials able to withstand these conditions are thus critical to the performance of downhole tools.
Historically, the oil and gas industry has relied primarily on steel for manufacturing downhole tools. With the advent of high speed turbines, as well as harsher drilling environments, higher stresses and strains are being placed on downhole tools. Accordingly, materials that exceed the durability of steel are needed in many applications, particularly in drill bits and turbine sleeves placed adjacent to drill bits.
In some applications, a turbine sleeve may be placed adjacent to a downhole drill bit. A turbine sleeve is typically a substantially cylindrical structure with a series of blades running along its outside diameter and contacting the borehole. A series of channels running between the blades allow drilling fluids to pass by the sleeve. The turbine sleeve extends the gauge portion of the drill bit and is helpful to reduce lateral movement of the drill bit and prevent the hole from going undergauge.
The sleeve may also reduce vibration and hole-spiraling in order to provide a consistently smooth, concentric borehole. The smoothness of the borehole may be critical to placing casing and obtaining accurate logging data. The sleeve may improve rate-of-penentration (ROP) and bit life, thereby extending drilling time and decreasing tripping frequency.
Typical turbine sleeves may be may be made of various materials or combinations of materials. In some cases, turbine sleeves may include an internal steel structure that is coated with a matrix material, such as a tungsten carbide matrix. Nevertheless, conventional matrix-coated sleeves are known to be susceptible to blade fractures at the matrix/steel interface due to residual, mechanical, and thermal loading, thereby significantly limiting their service life.
In view of the foregoing, what are needed are improved matrix-coated turbine sleeves that are less susceptible to blade fractures and that can better withstand residual, mechanical, and thermal loading. Further needed are improved methods for making matrix-coated turbine sleeves.